> I really do not want to be a stick-in-the-mud here, but what do we
base

> the idea that "copies" could exist upon?
It is a conjecture called "functionalism" (or one of its close variants).

"Functionalism," at least, in the social sciences refers to the proposition
that everything exists because it has a function (use). When that notion
came under attack in the 1960s, structural functionalists responded that
some things have "latent functions"--uses that we have yet to
divine. Functionalism follows Scholasticism which follows teleology. Not
particularly good science---or at least, not *modern* science.

> What if "I", or any one else's 1st person aspect, can not be copied?
> If the operation of copying is impossible, what is the status of all
> of these thought experiments?

Still pretty robust. If you accept that a chronon has a dimension equal to
about 10^-43 seconds, then you'd have to concede that we exist as a "deck"
of copies through time. No big deal, but we ARE copies of the individual we
were 1 x 10-^43 seconds ago. If not, where's the "glue"?

I notice that many people seek refuge in the "no-copying" theorem of
QM. Well, for them, I have that automobile travel also precludes
survival. I can prove that to enter an automobile, drive it somewhere,
and then exit the automobile invariably changes the quantum state of
the person so reckless as to do it.
If someone can teleport me back and forth from work to home, I'll
be happy to go along even if 1 atom in every thousand cells of mine
doesn't get copied.

Exposure to a nuclear detonation at 4000 yds typically kills about 1 in a
million cells. When that happens, you die. I would suggest that is a bad
metaphor.

Moreover---I am not really picky about the exact
bound state of each atom, just so long as it is able to perform the
role approximately expected of it.

Structural functionalism. When physicists converse at a bar, they talk the
language of sociology.

(That is, go ahead and remove any
carbon atom you like, and replace it by another carbon atom in a
different state.)
> If, and this is a HUGE if, there is some thing irreducibly quantum

> mechanical to this "1st person aspect" then it follows from QM that
copying
> is not allowed. Neither a quantum state nor a "qubit" can be copied
without

> destroying the "original".

What if there is *no* original copy? Those that are familiar with
Photoshop would probably argue that each layer created is still an integral
part of the image. If you accept Cramer's transactional model, then what
*will* take place in the future will affect the state of the past. You
don't suppose Julian Barbour is on to something?